1. Field of the Invention
The present invention relates to a method of producing a copper-silver (Cu--Ag) alloy based conductive material employable for high field magnets such as long pulse magnets or the like.
2. Description of the Related Art
In recent years, various research, which uses a high intensity of magnetic field, has been widely conducted in the fields of physics, engineering, medical science and other areas of technology. Consequently, corresponding development efforts have been intensively conducted for providing magnets having high intensity magnetic fields. Due, at least in part, to such efforts, a novel Cu--Ag alloy with a high strength and high conductivity has been developed. This material is expected to be utilized as a raw material for a so-called long pulse magnet which generates a very high magnetic field in excess of 80T with a longer duration time of several milliseconds to several ten milliseconds. The long pulse magnet is used for investigating the phenomena of superconductivity.
The conventional Cu--Ag alloy is produced by way of the steps of casting a copper (Cu) based alloy containing about 10 to 16 at % of silver (Ag) by an ingot casting process, hot-forging the casted ingot at a temperature of 450.degree. C., intermediate heat treatment at a temperature of 400.degree. C., or 450.degree. C. for 2 to 10 hours, grinding or facing, and finally cold-drawing
However, it has been found that the conventional conductive Cu--Ag alloy produced in the above-described manner has the following drawbacks.
Since hot-forging can process a small amount of alloy at a time due to a restricted temperature range, heating and forging must be repeated many times. Since flaws are likely to appear on the surface of the alloy during each hot-forging, there arises the necessity for facing the surface, resulting in the low yield and high cost. When producing large ingots to be used for drawing a long wire, segregation occurs easily in the casting process, and moreover the cast ingot is liable to crack during hot-forging Another drawback is that it is difficult to produce wires with a small diameter. When the ingot casting process is employed, the slow rate of cooling will cause precipitation in the ingot, which leads to a failure in the stable production of the materials with expected conductivity and strength. The drawback appears more remarkably in the production of large size ingots.